1. Field of the Invention:
The present invention relates to a method of producing a cylindrical stator which is used in a rotary machine such as an inner-rotor electric motor.
2. Description of the Prior Art:
Stators for use in the conventional inner-rotor electric motors have been produced by the so-called insert method. In this method, coils are first prepared by winding coil wires on a frame, and then the resultant coils are inserted into the slots between teeth formed on the inside of a cylindrical stator core, resulting in a stator.
In this insert method, the shape of each coil previously prepared must be adjusted before it is inserted into the slots through slits between the ends of the teeth. After insertion, the portions of the coils which protrude out from the upper and lower ends of the stator core are appropriately shaped and secured in place, and lead wires are prepared and attached to the ends of the coils. In this way, this method requires many processes for mounting the coils on the stator core, thereby complicating the production, reducing productivity and making it difficult to automate the production process of the stator.
Another type of stator core for a stator has been proposed by Japanese Laid-Open Patent Publication No. 58-33945. The stator core comprises a main core unit, on the outside of which a plurality of protruding teeth are formed, and a ring unit which fits on the outside of the main core unit. In the production of this stator core, a coil wire is repeatedly passed through the slots between the teeth to form coils on the outside of the main core unit by a flyer winding technique, etc.
In this method, the coil wire is directly formed on the outside of the main core unit, so that coils need not be inserted in the slots and the processes required before and after the insertion are not necessary. This simplifies the production process, but the complicated work for preparing the lead wires for the coils is still necessary, which makes it difficult to automate the production.